1. Field of the Invention
This invention relates to a novel caliper. More particularly, the invention relates to a self-positioning caliper requiring no use of hands for positioning the same. Thus, both hands can be used to hold the object to be measured and the measurement is performed under a precise pressure.
2. Brief Description of the Prior Art
Digital vernier calipers are known in the art. They are similar to the regular vernier calipers using a measuring scale or a dial, but they use a electronic measuring unit with a digital display of measured values and with a possible interface for connection to a computer and/or printer to provide means for storing and/or printing the measurements. All these calipers are positioned for measurement by hand either by moving the measuring jaw away from and then towards the stationary jaw or by a thumbwheel jaw movement, whereby the measuring jaw can be moved with a thumb of the same hand that holds the caliper, leaving the other hand free to insert the object to be measured.
The problem with such calipers is that the measurement depends on the force exerted by the person measuring the dimension of the object; consequently when measuring, for example, the diameter of a plastic bottle or other container it is almost impossible to get accurate repetitive readings. By exerting even a slightly stronger pressure than during a preceding measurement, the plastic container will yield inwardly and the measurement reading can then easily exceed the acceptable standard in the industry of 0.007" variation. Also when different operators perform the measurements, there is even greater possibility of having erroneous readings. It should also be noted that, for example, in the plastics industry, when objects such as bottles, containers and the like, are manufactured, the plastic is not completely solidified for a period that may last up to twenty four hours and it is often important to measure the dimensions of such objects while they are still somewhat soft. Again, with known calipers this is very difficult to do, since even the slightest variation in the force exerted on the measuring jaw may greatly distort the reading.
The need of a precise measuring force is recognized, for example, in U.S. Pat. No. 4,924,598 of May 5, 1990 , which discloses a height measuring instrument with a fairly complex arrangement to produce a desired measuring pressure between a measuring pin and the article to be measured. Such arrangement would not be applicable to a caliper.
Another problem with the known calipers is that they must be held in one hand while the article to be measured is held in the other hand and is then inserted between the jaws of the calliper to effect the measurement. However, if an article is such that it must be held with both hands to be measured, then the known calipers cannot be used, unless two people perform the measurement, one holing the article to be measured and the other effecting the measurement with the caliper. This, of course, would be quite inefficient.